My question is simple. How hard it would be to fabricate a Battery of customized shape say of 30cm x 30 cm x 0.5 cm that can be fabricated by DIY without requiring any specialized/ hazardous chemicals or manufacturing processes that can be easily fabricated in garage setup with upto 500mA operating current and capacity in mAH range upwards of hundred? Does anyone know any chemistry that can achieve this?
Are there any battery chemistries that can be fabricated at home
batteriesbattery-chemistry
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According to this video it is possible to make a zinc-air battery. I just don't know if it is rechargeable.
You just need a zinc sheet for the negative electrode, and a steel wool for the positive electrode separated by an isolator soaked in sodium hydroxide as an electrolyte.
Update
I've been reading a little about zinc-air batteries and I can confirm that this configuration does not produce a rechargeable battery.
The rechargeable zin-air battery technology is a very recent one and I don't believe that we can find anything about how to do it at home in the recent future.
I very seldom disagree with Olin technically. In this case there may be special circumstances which make part of his advice correct in general but specifically wrong in this case.
As he notes, first it is necessary to establish the voltage across the battery to ensure it is in fact a single cell and not a number in series. As you say that the razor operates OK on the new battery then it is extremely likely that the old one is also a single cell.
15 VDC at 420 mA sounds just plain wrong. The voltage is high by a factor of about ten times, so maybe it's 1.5V.
For a 2300 mAh cell the 420 mA would be C/(2300/420) ~= C/5.
This is an OK charging rate BUT if the charging is not COMPLETELY terminated when the cell is charged the cell will "cook" in short order.
For capacities up to 1500 mAh, maybe 1800 mAh NimH calls had special arrangements (chemicals and structures) which allowed recomination of Hydrogen when "gassing" occurred when a cell was left on charge when fully charged. This allowed manufcxaturers to specify a trickle-charge rate of say C/10 (230 mA for a 2300 mAh cell). At or below this rate the cell could be left on charge indefinitely with little or no damage. HOWEVER as the typical battery capacity arms-race occurred and capacities were pushed up to 2100 2300 many_lies 2500 2600 all_lies ... mAh the manufacturers looked for more space to fit active material into. Something had to go, and it was the gas recombination mechanism. Modern NimH cells above about 2000 mAh from reputable manufacturers have data sheet advice of the form:
- Do not trickle charge at all! or
Trickle charge at no more than C/20 or whatever for some_very_small_period or
Can be trickle charged at <= C/100 on a good day downhill with the wind behind you.
Any battery manufacturer whose data sheet says ... 2500 mAh ... trickle charge at <= C/10 can be safely shunned as a source of supply for all future time.
SO when Olin says " ... In that case, the highest capacity battery is best since it will be abused less at the same current." - this is good advice in the general case BUT not so when using NimH where the charger is badly behaved. In such cases use of an older style 1500 mAh cell would probably [tm] give a much longer life.
However - IF the charger really is a true 1.5V charger and if this is tightly controlled (rather than edging upwards as load current drops, then it MAY be OK.
At say C/10 the terminal voltage of a NimH cell at room temperature at the end of charge will be ~= 1.45 V. 1.4 is safer and 1.5 is a bit high. Actual value varies slightly with manufacturer. Temperature much above 25C vary this voltage BUT also are best avoided. Higher charge rate lead to higher voltage st end of charge.
SO - measure charger output. If it is 1.5V and no more your battery may last OK. If it rises to > 1.5V at light loads you MAY be able to load it down with a suitable resistor. But using a 1500 mAh cell is probably wise.
Added:
The 1.46 Volts after 4 hours sounds very good. That's 420 x 4 = 1680 mAh BUT the 1.46 volts sounds like a fully charged cell so presumably the cell was partially or filly charged originally.
Try an overnight charge - if it's still at 1.46V they seem likely to have done a reasonable job of charge control.
If you are able to measure the battery current on charge at the end of an overnight charge you will be able to tell if it is trickle charging. This can be accomplished by eg a battery interceptor / continuity break insulator against the +ve battery terminal and add a conductor on either side and take wires out to an ammeter. OR locate the battery externally and bring out two wires to it via an ammeter.
Here's an example of a battery interceptor, From here
= http://www.instructables.com/id/Remote-Power-Control-For-Battery-Powered-Devices/
Best Answer
There are - or were - but this may not be the answer you want.
If you look at the September 1901 issue of "Model Engineer and Amateur Electrician" (now just "Model Engineer") you'll find full construction drawings for a 2-cell battery with (according to the article) a low internal resistance, using zinc and carbon electrodes, and "four ounces of chromic acid or bichromate of potash dissolved in 12ounces of water". All common materials, readily available from your local chemist (pharmacy) - at least, when it was written.
The battery had one interesting feature : to switch it on or off, you lowered the electrodes into the solution, or raised them.
To give some perspective, these instructions come from the heroic days of the magazine, when it was perfectly normal to build your own motorbike, casting and machining the engine's cylinder yourself.
This can be seen from the assembly instructions : "First well amalgamate the zincs by dipping them in dilute sulphuric acid, and then rubbing them over with mercury (use a piece of rag at the end of a stick for this)" - see the emphasis on safety here?
Lifetime? "If the lamp does not take more than 1/3 ampere, it should remain at full brilliancy for two hours right off", and "Renew solution when current weakens". (It's a primary cell, not rechargeable).
You would need to adapt this basic design to your form factor... though a slim tray full of LiPo cells is probably a lot easier.